Biological Transformation of Nitrogen Compounds

Our next task is to consider the various ways that nitrogen is processed by the biosphere. These 

Nitrogen fixation is any process in which Nj in the atmosphere reacts to form any nitrogen compound. Biological nitrogen fixation is the enzyme-catalyzed reduction of N2 to NH3, NHj, or any organic nitrogen compound. 

Ammonia assimilation is the process by which NH3 or NH4 is taken up by an organism to become part of its biomass in the form of organic nitrogen compounds. 

Assimilatory nitrate reduction is the reduction of NO3, followed by uptake of the nitrogen by the organism as biomass. 

Ammoniafication is the breaking down of organic nitrogen compounds into NH3 or NHJ. 

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Fig. 12-1 Biological transformations of nitrogen compounds. The numbers refer to processes described in the text.

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